Acid-charging system for digesters



F. J. DOOLEY.

ACID CHARGING SYSTEM FOR DIGESTERS.

APPLICATION FILED MAY 23. 1919.

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FRANCIS J. DOOLEY, 013 BOSTON, MASSACHUSETTS.

ACID-CHARGING SYSTEM FOR DIGESTEBS.

Specification bf Letters Patent.

Application filed May 23, 1919. Serial No. 299,152.

To all whom it may concern:

Be it known that I, FRANCIS J DOOLEY, a citizen of the United States, and resident of Boston,.in the county of Suffolk and State of Massachusetts, have invented an Improvement in Acid Charging Systems for lQigesters, of which the following is a specification. 3

My invention relates to the manufacture of pulp from cellulosic material and has particular reference to an acid charging system by which the digesters are charged. with the pulp-forming liquid, usually bisulfite liquor.

The bi-sulfite liquor contains a considerable proportion of free sulfur dioxid and also solid material due to its method of manufacture.

In charging the digester with acid through the bottom, in accordance with one method, the solid matter contained in the acid cuts the seats of the valves located in the acid conductor at thebase of "the digester and causes loss of acid by back flow therethrough during the subsequent steaming operation. I

The valve cannot be opened for packing, after the chargingv operation has been completed, because of the back flow of acid due to its head in the digester.

In charging the digester with acid throughv the top, sulfur dioxid gas escapes therefrom. in such quantities as to have a very deleterious effect upon the digester attendants and also results in considerably increasing the consumption of sulfur per ton of pulp.

The object of my invention is an improved means for charging a digester with the pulp-forming liquid in which the faults above enumerated are obviated; whereby the piping associated with the digester is simplified; and whereby the control of the acid charging operation is facilitated.

In the performance of my invention I introduce the acid through the bottom of the digesters whereby the escape of obnoxious gas is avoided. I extend a pipe from the acid main to the bottom of the digester and so arrange said pipe that a suitable extent thereof is above the top of the digester, or at least above the level to which the digester isadapted to be filled with acid and in this elevated portion of the acid pipe I insert the acid control valve. Due to this arrangement, after the digester has been filled with acld, the control valve may be opened or loft, not shown.

disassembled and packed to render it tight during the cooking operation without the escape of acid from the digester because of the position of said valve above the level of acid in the digester. The choking or plugging of the acid pipe with chips or pulp Patented. Apr. 27, 1920'.

by the back flow of acid in the pipe is obviously obviated by the provision of a tight acid valve.

Although I may introduce the acid into the digester through a separate acid line I prefer to introduce the acid through the steam line through which steam for the cooking operation is supplied to the digester by which the cost of the piping is reduced and certain other advantages accrue therefrom.

Figure 1 is a preferred embodiment of my invention associated with a battery of digesters.

Fig. 2 is a modified form of my invention.

As-shown in Fig.- 1 my invention is associated with a battery of digesters of which two are illustrated. Each digester 10 is of at the top of each digester through which the cellulosic material as wood blocks or chips may be introduced within the digester from the chip spout 12 arranged above the neck opening and extended from the chip After the digester has been more or less completely filled with chips and acid the neck is closed by the cover 13 which is securely bolted thereon. The lower end of the digester is of conical form, as indicated at 14, and terminates in a blow-off T 15 secured thereto. blowofi' pipe 16 in which the valve 17 is included is in communication with said T and serves to conductthe pulp to a suitable pulp receiver upon the opening of said valve 17 at the expiration of the cooking period.

Steam, supplied from a boiler, not shown, is admitted to the digester for the cooking 'of the contents thereof through the steam bottom of the digesters and near the blowoff T. A check valve 24 arranged to permit the flow of steam into the digester and to prevent the flow of liquid from the digester through said pipe is also included. in said pipe between said valve 23 and the digester.

A conductor 25 is in communication with the lower part of the branch pipe 21 and the blow-off T of the digester in which is included the control valve 26 and check valve 27 and forms an end steam line which serves to cause the gas remaining in the digester at the expiration of the blow-off to be discharged through the blow-off pipe 16.

The arrangement of apparatus above described is more or less usual in the art. In the performance of my invention I extend an acid main 30 along the length of and preferably above the top of the digesters or at least above the level to which the digesters are adapted to be filled with acid.

aid main 30 is in communication with a pipe or conductor 31 extended to a pump 32 of any suitable type driven by a suitable motor 33. Said pump receives acid from acid storage tanks, notv shown, through the inlet pipe 34: and discharges acid into the main 30. At each digester a separate acid branch pipe 35 (Fig. 2) extends between said main 30 and the steam branch pipe 21 for the flow of acid from said acid main into the digester through said steam branch pipe. An acid control valve 36 is included in said acid branch pipe 35 by which the flow of acid into the digester may be controlled. Said acid branch pipe 35, or at least that portion in which said valve 36 is included, is adapted to be' above the level to which the digester is adapted to be filled with acid whereby said valve is also above .said level, which is an essential feature of my invention.

Said valve 36 is of the angle type of more or less common construction and has an opening therein normally closed by the plate 37 which may be removed for access to the.

valve seats to renew or renovate said seats after the acid'charging operation and before the cooking operation.

In the modification illustrated in Fig. 2 the acid branch pipe 35 is not connected with the branch steam pipe 21 near the top of the digester but is extended as an independent conductorv to the bottom of the digester and may be independently connected with the digester for the discharge of acid therein in a manner that is obvious or it may be connected to said steam branch pipe 21 between the control valve 23 and check valve 24 whereby the piping is some- I what simplified. In'so far as the operation of the system is concerned the modifications are identical. j

Referring to Fig. 2, previous. to the charging of the dige'sterswith acid they have been filled to the top with chips and the filling neck 11 remains open. The pulp blow-off valve 17 has been closed and the main steam valve 22 is closed, and the valve 23 is open. The acid valve 36 is opened and the acid is drawn from the tank, not shown, by the pump 32 and flows through the acid main 30, branch pipe 35, and acid valve 36, into the steam branch pipe 21, and through the valves 23 and 24 therein into the digester which it fills to some level below the opening at the top thereof and expels by displacement the air contained therein. Relatively little gas escapes from the digester by reason of its being absorbed by the wood chips contained therein and of its relatively great weight. After the completed acid charging operation, the valve 36 is closed and the acid pump is stopped. The valve 36 may now be opened and access to the interior of the valve for packing or renewal of the valve seats may be had by removing the plate or cover 37 whereupon, with certain types ofacid pumps, the acid contained in the pipe 31 will drain through the pump to the acid storage tank or with certain other types of pumps acid will be retained in the pipe. By reason of the location of th e valve 36' above the level of acid in the. digester there can be no discharge of acid from the digester through the open valve or its casing and therefore the acid will be retained in the digester. The valve 36 is then made fluid tight by inserting a gasket of suitable packing material between the valve seats and the cover plate 37 is replaced in secured position on the valve casing. .Said valve is now closed and the steam valve 22 is opened and steam is admitted to the digester for the cooking of the contents. Because of the flow of steam through said pipe 21, it is cleared of its acid contents and plugging of the lower portion thereof with pulp and wood chips is prevented. After the completion of cooking the digester is blown oil in the usual manner.

It is to be noted that by the provision of the inlet for acid to the digester at the bottom thereof and the acid control valve above the acid level in the digester the .digester may be charged with acid without escape of obnoxious acid gas, and thevalve is maintained tight during the entire cooking process. It is also to be noted that by the provision of the acid valve at the top of the digester the charging operation may be controlled from the charging floor whereby the necessity of an attendant at the bottom of the digester during this operation is obviated and the acid charging process thereby facilitated and rendered less expensive.

below the acid level of the digester, an acid conductor in communication with said forcing means and extended to the digester and in communication with the interior of the digester below the acid level thereof, said conductor having a length thereof elevated above the acid level of the digester, and an acid control valve included in such elevated length of the conductor.

2. In an acid charging system for digesters, an acid conductor adapted for communication with an acid supply and extended to and in communication with the digester below the acid level thereof, said conductor having a portion thereof elevated above the acid level of the digester, and an acid control valve included in such elevated portion of the conductor.

3. In an acid charging and steaming system for digesters, a steam conductor adapted for connection .with a source of steam supply havin a portion thereof elevated above the aci level of the digester and extended downward and in communication with the interior'of the digester below the acid level thereof, an acid conductor. adapted for connection with a source of acidsupply having a portion thereof elevated above the acid level of the di ter and in communication with the sim1 arly elevated .por-

tion of the downwardly extended steam conductor, and an acid control valve in- .cluded in the'elevated portion of the acid FRANCIS J. DOOLEY.

Witnesses:

H. B. DAVIS, T. T. Gmmvooo. 

